As protection maloperation caused by digital sampling in electronic inductors, collector circuits and merging units of smart transformer substations become more and more frequent, and fault location and analysis is difficult for a Sampled Value (SV) digital sampling circuit, the digital sampling becomes significantly inferior to conventional sampling.
For example, Chinese patent No: 201410667282.0 titled “Protection Measurement and Control Integrated Device and Protection Measurement and Control Method” discloses a protection measurement and control integrated device, including a Man Machine Interface (MMI) plug-in, a New Process layer Interface (NPI) plug-in, a protection Central Processing Unit (CPU), a measurement and control CPU and an Input/Output (I/O) plug-in, wherein the NPI plug-in is used for receiving sampled data and GOOSE information from a merging unit. It can be seen that the sampled data provided for logical judgment of the protection device is from the merging unit, and thus protection maloperation caused by the digital sampling also exists.
In addition, chassis sampling in a conventional sampling GOOSE trip mode uses single-protection CPU operation mode, and reliability of a protection sampling circuit is not high, thereby easily causing protection maloperation.